1. Field of the Invention
The present invention relates to a power supply control device used in an electric control unit (ECU) of electric equipment for a vehicle and more specifically to a power supply control device provided with high precision time correction and clock functions.
2. Description of the Related Art
In recent years, the electric control unit (specially, for automobiles) mounted to a vehicle is provided with a power supply control device for converting an ordinary standard battery voltage of 12V to various voltages of 5V and 3.3V or the like and then supplying these generated voltages to other devices loaded for electric systems such as an microcomputer and various sensors.
This power supply control device is requested to have a function to measure the period in which the engine operation has stopped using a timer circuit provided, a function to run an evapo-leak diagnosis to a fuel tank loaded to the vehicle by activating the microcomputer and various sensors after passage of the specified constant period after the engine operation has stopped, and a function to run a diagnosis for various temperatures during passage of the time in which the engine operation has stopped. Particularly, in the case of an electric vehicle, the power supply control device is requested to provide a function to administrate the present time, because it is required that the battery is charged after the vehicle has learned, for the charging of battery, that the electricity charges are lowered at the midnight hours and a driver (owner, user) uses the vehicle less during such a period.
Moreover, the electric control unit is also requested to provide a function to compute life-time of the vehicle or learn running conditions and a using period. In addition, it is also requested to have a function to collect and record failure occurring time and period.
As the prior art of providing the time management function to satisfy the requirements explained above, it is possible to list up, for example, a control unit with time correcting function (refer to Japanese Patent Application Laid-Open Publication No. 2005-114585) providing a section that computes life-time of the vehicle, automatically correcting the time, and always recognizing the highly accurate absolute time.
In the control unit with time correcting function of Japanese Patent Application Laid-Open Publication No. 2005-114585, a timer circuit having the function to generate a clock utilizing charging and discharging of a capacitor is provided within a power supply control device (control device) to constitute a section that corrects time management by receiving time data from the standard radio wave as a section that recognizes the accurate absolute time.
However, in the case of this function structure, if there is an obstacle in an underground parking lot and garage while a vehicle is parked, it is no longer possible to normally receive the standard radio wave. In this case, the accurate clock for measuring the present time and the period while the engine operation is stopped cannot be acquired. As a result, the highly accurate time correcting and clock functions cannot be maintained, resulting in problems that control and execution of various functions based on the accurate time management are disabled.
The present invention has been proposed to solve the problems described above and a technical subject of the present invention lies in providing a power supply control device for maintaining highly accurate time correction and clock functions and actualizing control and execution of various functions based on accurate time management under any application environment.